In the rat brain biochemical changes in choline acetyltransferase (CAT) following stereotaxic lesions revealed that cholinergic nerves of the nucleus of the tractus diagonalis project to the cortex (frontal, cingulate, entorhinal, occipital), hippocampus, amygdala, dorsomedial nucleus, lateral habenula, globus pallidus, anterior ventral nucleus of the thalamus and interpeduncular nucleus. The nucleus tractus diagonalis is a major cholinergic nucleus that projects long descending neurons to regions of the forebrain, midbrian and hindbrain.